Solar PV Code Comparison

A Solar Installer's Guide to DC Cable Sizing Across Three Codes

One installer working projects under different codes needs one consistent mental model for PV DC cable sizing — here is that model, mapped to each code.

Solar installers increasingly work across borders and across specifications — a Philippine EPC contractor bidding on an Australian-standard project, or a designer producing documentation that has to satisfy more than one code's reviewer. Having one consistent mental model for DC cable sizing, mapped to each code's specific terms, makes that kind of cross-code work far less error-prone.

The Universal Five-Step Process

Pull module Isc from the datasheet — this is your starting point regardless of code
Apply the applicable safety multiplier — a ~1.25× factor appears in some form under PEC, AS/NZS 5033, and NEC Article 690, though the exact figure and any additional stacked factor vary by code (see the dedicated 1.25×Isc article)
Select conductor size against the derated ampacity requirement — base table figure, corrected for the installation's real ambient temperature and any grouping with other current-carrying conductors
Check voltage drop against the DC-specific limit — typically tighter than general AC limits under every code, usually in the 1–3% range
Verify isolator, connector, and protective device ratings against the same array voltage and current figures used for the cable itself

Where the Codes Diverge Enough to Matter

Code	What's distinctly different
PEC	Metric conductor sizes (mm²); tables and safety factor presentation specific to Philippine practice
AS/NZS 5033	Explicit maximum system voltage limits by installation type (600V residential / 1000V commercial / 1500V ground-mount, broadly); detailed DC isolator and labelling requirements beyond just cable sizing
NEC Article 690	AWG/kcmil conductor sizing; distinguishes PV source circuits from PV output circuits explicitly; continuous-load provisions can stack into an effective ~1.56× multiplier in some calculation approaches

The Discipline That Prevents Cross-Code Errors

Never carry a "this is roughly what I used last time under a different code" conductor size into a new project governed by a different standard. Re-run the full five-step process against the specific code that actually governs the current project — every time, no exceptions for familiar-looking system sizes.

Work through your array's actual figures under whichever code applies in the OhmWorks PV/Solar DC Cable Sizing calculators — PEC, AS/NZS, and NEC tabs.

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